Attitudes are learned, but new research shows that differences between people in many attitudes are also partly attributable to genetic factors.

These include attitudes as diverse as whether one likes rollercoaster rides to controversial social issues such as attitudes toward abortion and the death penalty for murder.

The findings appear in this month's American Psychological Association's (APA) Journal of Personality and Social Psychology.

Study authors James M. Olson, Ph.D., Philip A. Vernon, Ph.D. and Julie Aitken Harris, Ph.D., of the University of Western Ontario and Kerry L. Jang, Ph.D., of the University of British Columbia, surveyed 336 pairs of adult Canadian twins (both fraternal and identical) to explore the role of genetic factors in creating differences between individuals in attitudes.

By comparing the responses to attitude questions between the identical and fraternal twins, (for example, "My overall attitude toward doing crossword puzzles is" with answers ranging from "extremely unfavorable" to "extremely favorable") the researchers were able to determine which attitudes were more influenced by genetic factors.

Of the 30 individual attitude items on the survey, 26 showed some genetic influence. The five which produced the largest genetic connection were attitudes toward reading books, abortion without restrictions, playing organized sports, rollercoaster rides, and the death penalty for murder.

The four items found to have no genetic effect were attitudes toward separate roles for men and women, playing bingo, easy access to birth control and being assertive.

Putting the individual attitude items into broader categories, the three factors having the largest genetic influence were attitudes toward the preservation of life (including attitudes toward abortion without restrictions, voluntary euthanasia and organized religion), attitudes toward equality (including attitudes toward making racial discrimination illegal, open-door immigration policies and getting along well with others), and attitudes toward athleticism (including attitudes toward doing athletic activities, playing organized sports and exercising).

Given that direct gene-to-attitude connections are extremely unlikely, what are the mechanisms that might account for the genetic component of attitudes?

The authors found that several personality traits and related characteristics -- themselves highly heritable -- may play a role. Sociability, in particular, showed a strong genetic connection with several attitudes. Athletic ability and physical attractiveness also produced significant genetic connections with certain attitudes.

"Presumably, these characteristics predisposed individuals to form particular kinds of attitudes, thereby contributing to the genetic determination of individual differences in those attitudes," said the researchers. "For example, a person with inherited physical abilities such as good coordination and strength might be more successful at sports than less athletically inclined individuals, resulting in the more athletic person developing favorable attitudes toward sports."

The authors say it's important to keep in mind that nonshared environmental factors (unique experiences of each member of a twin pair) had the most powerful contribution to attitudes. However, they add that more research is needed on the role of biological influences, including genetic factors, in the formation and change of attitudes.

"In the long run," they write, "we stand to gain the most understanding from perspectives that integrate biology and experience in accounting for individual differences." - By David Partenheimer

(Reference: "The Heritability of Attitudes: A Study of Twins," James M. Olson, Ph.D., Philip A. Vernon, Ph.D., and Julie Aitken Harris, Ph.D., University of Western Ontario, and Kerry L. Jang, Ph.D., University of British Columbia; Journal of Personality and Social Psychology, Vol. 80, No. 6.)

(Editor's Note: The full text of the article is available at this URL.)